Eleven bakers and 4 pastry cooks with hypersensitivity to wheat flour underwent skin tests to flours (wheat, barley, rye, oats), pollens (wheat, barley, rye, oats, grasses), mites (dermatophagoides pteronyssinus, dermatophagoides farinae), molds (alternaria, aspergillus) and weeds (parietaria judaica). The levels of serum immunoglobulins (IgG, IgA, IgM and IgE) were studied and the values of specific IgE (RAST) in the presence of wheat flour and the histamine release test for wheat flour, grass pollens, mites, molds and weeds were assessed. All the patients underwent a nasal challenge test to wheat flour. The results demonstrated the existence of cross reactions between the extracts of barley and rye flour with wheat flour (15/15) as well as between the pollens of cereals and cereal flours. The levels of specific IgE (PRU greater than .35) and the percentages of histamine release (greater than 10%) were positive in 14/15 cases. The nasal challenge test was positive for all the 15 patients under study. Of the patients studied, 11 received immunotherapy for periods ranging from 12 to 18 months. Of these patients, 9/11 continued working in the same occupation whereas the 2 who left their jobs in the industry corresponded to the cases of severe asthma which were polysensitized (flour, mites, molds).